Integrated circuits and other discrete circuits often include a power supply often labeled VDD that provides a source voltage for the associated circuitry. A circuit, for example an inverter, is often connected between the supply and circuit common or ground. In the case of MOSFET transistors, a specified voltage at a gate terminal activates the transistor to create a circuit path to drive circuit elements connected between an output terminal and the supply or ground and to drive the operation of subsequent circuits connected to the output terminal. Typically, the amount of current and circuit loading is related to both the operation speed and power supply voltage. Because of the active nature of many circuits, the loading will sometimes vary and, at times, may cause a supply voltage level to drop or be lowered from the desired level.
Voltage droop is a term used to refer to the drop in voltage from the desired voltage level as the supply drives a load. In a regulated system, the output voltage can sag when a load is suddenly increased very rapidly. For example, a transient loading condition may occur causing a voltage droop. If the droop is too large, then circuit failure results.
In prior art systems, supply adjustment circuits, or “header” circuits, are operably disposed between a supply and a circuit and are regulated to adjust or compensate for such variations in the supply. For example, some solutions include header circuits that constantly switch at a relatively high frequency above 1 GHz to minimize the loading from the transient response and to regulate the supply voltage. These header circuits are often optimized to respond very quickly to voltage droops due to transient loading conditions and other loading conditions.
These prior art systems typically have substantial customized analog design blocks and add significant overhead as they switch in and out of connecting relatively large field effect transistors in order to respond to transient loading conditions. This even occurs when operating in a steady-state mode. Thus, such systems not only consume precious integrated circuit real estate, but also are inefficient from a power perspective.
The use of the same reference symbols in different drawings indicates similar or identical items. Unless otherwise noted, the word “coupled” and its associated verb forms include both direct connection and indirect electrical connection by means known in the art, and unless otherwise noted any description of direct connection implies alternate embodiments using suitable forms of indirect electrical connection as well.